Scientists at University College London (UCL) have discovered a 4.2 billion-year-old fossil which gives convincing evidence that organisms once lived, and could again live, on Mars. Their research was co-funded by NASA and published in the journal Nature.

The microscopic bacteria, which is hundreds of millions of years older than existing specimens, were discovered in the Nuvvuagittuq Supracrustal Belt- a formation in Quebec which contains some of the oldest sedimentary rocks in the worl